2 research outputs found
Neutrino masses and cosmic radiation density: Combined analysis
We determine the range of neutrino masses and cosmic radiation content
allowed by the most recent CMB and large-scale structure data. In contrast to
other recent works, we vary these parameters simultaneously and provide
likelihood contours in the two-dimensional parameter space of N_eff}, the usual
effective number of neutrino species measuring the radiation density, and \sum
m_nu. The allowed range of \sum m_nu and N_eff has shrunk significantly
compared to previous studies. The previous degeneracy between these parameters
has disappeared, largely thanks to the baryon acoustic oscillation data. The
likelihood contours differ significantly if \sum m_nu resides in a single
species instead of the standard case of being equally distributed among all
flavors. For \sum m_nu=0 we find 2.7 < N_eff < 4.6 at 95% CL while \sum m_nu <
0.62 eV at 95% CL for the standard radiation content.Comment: 8 pages, 2 figure
Cosmology of neutrinos and extra light particles after WMAP3
We study how present data probe standard and non-standard properties of
neutrinos and the possible existence of new light particles, freely-streaming
or interacting, among themselves or with neutrinos. Our results include: sum
m_nu < 0.40 eV at 99.9% C.L.; that extra massless particles have abundance
Delta N_nu = 2 pm 1 if freely-streaming and Delta N_nu = 0 pm 1.3 if
interacting; that 3 interacting neutrinos are disfavored at about 4 sigma. We
investigate the robustness of our results by fitting to different sub-sets of
data. We developed our own cosmological computational tools, somewhat different
from the standard ones.Comment: 18 pages, 8 figures. Added in v2: an explicit comparison of our code
with CAMB, some clarifications on the statistical analysis and some
references. Matches version published in JCA